test: add comprehensive test coverage and improve code quality

- Add new test files for auth, service, and handler modules
- Improve test organization and coverage
- Refactor code for better maintainability
- Add captcha, settings, stats, and theme handler tests
- Add auth module tests (CAS, OAuth, password, SSO, state)
- Add service layer tests for auth, export, permissions, roles
- All Go tests pass (exit code 0)
- All frontend tests pass (325 tests in 59 files)

internal/pkg/antigravity/request_transformer_test.go

@@ -56,7 +56,6 @@ func TestBuildParts_ThinkingBlockWithoutSignature(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			toolIDToName := make(map[string]string)
 			parts, _, err := buildParts(json.RawMessage(tt.content), toolIDToName, tt.allowDummyThought)
-
 			if err != nil {
 				t.Fatalf("buildParts() error = %v", err)
 			}

internal/pkg/geminicli/oauth_test.go

@@ -520,7 +520,6 @@ func TestEffectiveOAuthConfig_ScopeFiltering(t *testing.T) {
 	cfg, err := EffectiveOAuthConfig(OAuthConfig{
 		Scopes: "https://www.googleapis.com/auth/cloud-platform https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/generative-language.retriever https://www.googleapis.com/auth/drive.readonly https://www.googleapis.com/auth/userinfo.profile",
 	}, "google_one")
-
 	if err != nil {
 		t.Fatalf("EffectiveOAuthConfig() error = %v", err)
 	}